1. Field of The Invention
The present invention relates in general to a wire saw used for cutting stone, concrete and the like, and more particularly to a wire saw which prevents a gap from being formed between a cylindrical mount of each of abrasive sleeves and an elastic material layer, certainly provides a desired straightness of a wire rope owing to flow characteristic of resin according to a shape of the elastic material layer, and is made endless to form a loop by means of a clamping pipe having a similar outer shape to that of the wire saw, thereby improving the using life thereof.
2. Description of The Prior Art
With reference to FIG. 2 showing a wire saw which is disclosed in U.S. Pat. No. 4,907,564, entitled "WIRE SAW", and is of interest to this invention, the known wire saw generally comprises a plurality of abrasive sleeves 10 surrounding a wire rope 20 and being spaced at predetermined intervals longitudinally of the wire rope 20, and a cylindrical elastic material layer 30 of resin such as natural rubber, polyurethane or the like which is integrally formed between the abrasive sleeves 10 in such a manner as to surround the wire rope 20. Here, the wire rope 20 has to be disposed in order to have a desired straightness.
Each of the abrasive sleeve 10 comprises a substantially cylindrical mount 12, and an abrasive metal layer 14 circumferentially formed on the outer peripheral surface of the mount 12. The mount 12 is disposed as buried under the elastic material layer 30 and surrounding the wire rope 20, and made, for example, of stainless steel and has copper plating applied to at least the outer peripheral surface thereof. The abrasive metal layer 14 is formed by dispersing abrasive particles, such as diamond or carborundum particles, in a metal matrix.
As shown in FIG. 1 which is a diagrammatic view for showing a method of cutting concrete by a conventional wire saw, when it is desired to cut a concrete wall 60, first, through-holes 61 are formed in the wall 60 by a core drill or the like. Sequentially, the wire saw is passed through these through-holes 61 and entrained around a drive pulley 50 while it is made endless to form a loop. At this time, a clamping pipe is used to connect both ends of the wire saw to each other in order to make the wire saw endless. Here, the wire saw is adequately twisted before forming the loop. In result upon driving the wire saw by means of the drive pulley 50, simultaneously with rotating, the wire saw revolves. The concrete wall 60 is, therefore, cut by means of the abrasive metal layer 14 of the abrasive sleeve 10. As the cutting operation by the wire saw proceeds, the drive pulley 50 is moved along guide rails from a first position represented at the solid line of FIG. 1 to a second position represented at the phantom line of the drawing.
According to the above known wire saw, it is proposed that the clamping pipe comprises a threaded connecting sleeve. However, this type of clamping pipe has a disadvantage in that it may easily loose the clamping state thereof during the cutting operation and also requires a considerable burdensome work in making the wire saw be endless. Thus, the clamping pipe conventionally comprises, as shown in FIG. 3, a connecting pipe 40 into both hollow ends of which opposite ends of the wire rope 20 protruding from the opposite ends of the wire saw are inserted in order to contact with each other, then the assembly of the wire rope 20 and the pipe 40 is compressed by means of a conventional compressing device in order to make the wire saw be endless.
However, the known wire saw has disadvantages in that the bonding force between the abrasive sleeves 10 and the elastic material layer 30 is relatively weak, and also in operation, simultaneously with rotation owing to the torsion of the wire saw the abrasive sleeves 10 revolve at a revolution speed of about 20 m/sec, thus a separation of the abrasive sleeves 10 from the elastic material layer 30 easily occurs due to a relative abrasion therebetween.
In other words, the wire saw is, as described above, provided with the elastic material layer 30 integrally formed therewith between the abrasive sleeves 10 in order to space the sleeves 10 at the predetermined intervals and also provide the wire saw with flexibility. Hence, a gap easily occurs between the cylindrical mount 12 of each sleeve 10 and the elastic material layer 30, furthermore, the gap allows a foreign substance such as stone particles, cutting fluid and the like to easily enter, thereby causing the wire rope 20, not to speak of the elastic material layer 30 to be suddenly cut before completing the predetermined using life of the wire saw. In result, the known wire saw has disadvantage in that it can not provide a required reliability.
In addition, it is required that the wire rope 20 is longitudinally disposed in the wire saw in order to have the desired straightness. However, there is no means for causing the wire rope 20 to be reliably maintained in the longitudinal center of a mold for forming the elastic material layer 30, thus the wire rope 20 may be radially biased due to an injection pressure of resin during the injection molding of the elastic material layer 30 in the mold, thereby resulting in a bad longitudinal straightness of the wire rope 20 as shown in FIG. 2. Thus, the wire rope 20 of the wire saw tends to compensate the longitudinal straightness thereof during the revolution for performing the cutting operation so that there occurs unbalance in force distribution on the circumferential surface of the abrasive metal layer 14 of each abrasive sleeve 10 due to the longitudinal straightness compensating force of the wire rope 20, thereby resulting in an eccentric abrasion of the abrasive metal layer 14. In result, the known wire saw has a disadvantage in that the using life thereof is obliged to be shortened due to the eccentric abrasion of the abrasive metal layer 14.
Also, the connecting pipe 40 has to provide a desired clamping force for the loop of the wire saw so that it conventionally has a construction of relatively longer length than the distance between the abrasive sleeves 10 in order to provide the desired clamping force when it is compressed for making the wire saw endless. Thus, there may occur unbalance in the load distribution to the abrasive sleeves 10 due to the relatively longer length of the connecting pipe 40, thereby causing a relatively heavy load to be imposed on the abrasive metal layers 14 of the two abrasive sleeves 10 which are disposed at opposite ends of the connecting pipe 40. Furthermore, the connecting pipe 40 conventionally comprises a copper pipe or a stainless steel pipe which has a lower consume resistance than that of the abrasive metal layer 14 of the sleeve 10, thus it is more easily abraded than the abrasive metal layer 14 of the sleeve 10. In result, the known wire saw has a disadvantage in that the connecting pipe 40 thereof may be easily cut due to the unbalance in the load distribution to the abrasive sleeves 10 during the cutting operation and also the lower consume resistance thereof.